The present invention relates to a freshness-keeping device used preferably for preserving food such as, for example, fresh food, cakes or the like for a long period of time to keep the freshness.
Generally, a freshness-keeping device is used to keep the freshness of food or other material to be preserved (for example, decorations for food such as bamboo leaves, persimmon leaves or the like, leather articles, articles made of wood or bamboo, articles made of grass or straw or the like). Such freshness-keeping device is known in, for example, U.S. Pat. No. 4,802,574, JP-A-9-140363 and so on.
Such freshness-keeping device by conventional techniques is produced by, for example, impregnating a volatile freshness-keeping liquid including ethyl alcohol or the like as the main component into an adsorbent, and the adsorbent is formed by using natural pulp or the like in a form of rectangular flat plate-like shape or a small round rod-like piece.
For example, an adsorbent formed as a rectangular flat plate of 50 mm long, 30 mm wide and 2 mm thick, is covered at its upper and lower surfaces with a resinous film having a high impermeability to gas, and the freshness-keeping liquid held inside is gradually dispersed to the outside from only side surface portions of front and back directions and left and right directions.
Further, in an adsorbent of, for example, a round rod-like shape of 10 mm in diameter and 70 mm long, outer peripheral surfaces of the adsorbent are covered over the entire length with a resinous film having a high impermeability to gas, and a freshness-keeping liquid held inside is gradually dispersed outside from end portions at both ends in a direction of the length. In this case, the resinous film has a porous structure and such a treatment that the freshness-keeping liquid is gradually dispersed from the outer peripheral surfaces of the adsorbent, is conducted.
Such freshness-keeping device is used by putting it in a food packing body for a material such as fresh food, cakes or the like, and the freshness-keeping liquid in the adsorbent disperses gradually in the food packing body. Accordingly, the freshness-keeping device fills the space (head space) in the food packing body with a gaseous atmosphere for keeping the freshness, and the gas is adsorbed in a surface side of the food to thereby suppress an increase of bacterium such as mold.
Further, as another conventional technique (disclosed in, for example, JP-A-11-32743), an ethanol vapor generating sheet, a method of producing the same and a treating method for food are described. The ethanol vapor generating sheet by the other conventional technique has such a structure that a N-vinylcarboxylic acid amide series liquid absorbent containing ethanol or its aqueous solution is uniformly interposed between two envelope sheets at least one of which has ethanol vapor transmitting properties, four sides of the two envelope sheets are sealed by heat bonding in this state.
In the above-mentioned conventional techniques, however, a side surface and so on of the adsorbent of the freshness-keeping device in the food packing body may directly contact the food in the packing body whereby the freshness-keeping liquid in the adsorbent may be absorbed in the food in an early stage. Thus, there are problems that the service life of the freshness-keeping device decreases and discoloration of the food is caused to reduce the article value.
Further, in food containing much amount of fats and oils such as western cakes or the like, fats and oils in the food may be adsorbed in the adsorbent of the freshness-keeping device from its side face and so on. Accordingly, there are problems that the freshness-keeping device is discolored by the fats and oils of food adsorbed by the adsorbent, and a reduction of the quality of the outer appearance is resulted.
On the other hand, even in the ethanol vapor generating sheet by the above-mentioned another conventional technique, there may occur such problems that when the food or the like contacts directly an envelope sheet having ethanol vapor permeability, or when the food contacts a side edge portion of an envelope sheet, the ethanol or an aqueous solution thereof in the liquid absorbing agent is absorbed to the food in an early stage or the fats and oils in the food are absorbed into the liquid absorbing agent.
The present invention has been made in considering problems in the above-mentioned conventional techniques, and an object of the present invention is to provide a freshness-keeping device which prevents an adsorbent from contacting directly food or the like to keep the freshness of the food or the like in a stable manner for a long period of time.
Further, it is another object of the present invention to provide a freshness-keeping device capable of suppressing the absorption of fats and oils of food or the like in an adsorbent, thereby causing discoloration of the adsorbent and a reduction of the quality of the outer appearance, and capable of increasing the article value.
In the construction employed in the present invention in order to solve the above-mentioned problems, there is provided a freshness-keeping device for keeping the freshness of food or other material to be preserved, which comprises an adsorbent adsorbed with a volatile freshness-keeping liquid and a film cover made of a material having a high impermeability to gas of the freshness-keeping liquid, which has larger dimensions than the adsorbent to cover the adsorbent from the outside, wherein the cover has a skirt portion extending in a lateral direction of the adsorbent and a dispersing opening is formed at the skirt portion to permit the freshness-keeping liquid to gradually disperse outwardly from the adsorbent.
With such construction, the volatile freshness-keeping liquid adsorbed previously in the adsorbent gradually disperses from the dispersing opening formed at the skirt portions of the film cover to the outside, and the dispersing rate can be adjusted by the surface area of the opening. In this case, since the film cover has a high impermeability to gas volatilizing from the freshness-keeping liquid, there is no possibility that the freshness-keeping liquid in the adsorbent disperses from a portion other than the dispersing opening of the cover to the outside. Further, since the cover has the skirt portion having larger dimensions than the adsorbent to cover the adsorbent from the outside and extending in a lateral direction of the adsorbent, the direct contact of the adsorbent held inside to the food or the like can be prevented by the skirt portion of the cover, and the dispersing rate of the freshness-keeping liquid can correctly be kept by the dispersing opening.
Further, the present invention provides the construction that the extension dimension L of the skirt portion extending in a lateral direction of the adsorbent is larger than the thickness T of the adsorbent (L greater than T).
Further, the present invention provides the construction that the cover comprises a single or two films made of a material having a high impermeability each having larger dimensions than the adsorbent and having an outer periphery as the skirt portion extending in the lateral direction of the adsorbent in a state of sandwiching the adsorbent wherein the film or films secure the adsorbent by bonding upper and lower surfaces of the adsorbent in a state of sandwiching the adsorbent, and the skirt portions extend to an outer side of the adsorbent to provide a dispersing opening by being separated in upper and lower directions.
With such, the single or two films can hold the adsorbent in a state of sandwiching it, and each of the skirt portions is extended from the upper and lower surfaces of the adsorbent to an outer side with a space kept therebetween whereby the dispersing opening can be formed between them. Accordingly, the freshness-keeping liquid gradually disperses from side surfaces of the adsorbent sandwiched by the single or two films to the outside through the dispersing opening between the skirt portions, and the direct contact of the adsorbent to the food or the like can be prevented by the skirt portions.
Further, the present invention provides the construction that the cover comprises a single or two films made of a material having a high impermeability each having larger dimensions than the adsorbent and having an outer periphery as the skirt portion extending in a lateral direction of the adsorbent in a state of sandwiching the adsorbent, and a plurality of bond areas formed at the skirt portions, which are formed by bonding the skirt portions whereby the adsorbent is restricted between the film or films and wherein the dispersing opening is constituted by a non-bond area which is located between the bond areas between the skirt portions of the film or films.
With this, the single or two films are bonded at the plurality of bond areas formed at the skirt portions as the outer periphery; the bond areas can restrict the adsorbent in a state that the adsorbent is sandwiched between the films, and the adsorbent can be held at a position inside of the skirt portions of the films. Further, since the dispersing opening is provided by the non-bond area located between the bond areas between the skirt portions of the film or films, it is possible to gradually disperse the freshness-keeping liquid in the adsorbent to the outside through the dispersing opening.
Further, the present invention provides the construction that the adsorbent has a polygonal flat plate-like shape; the film or films have a shape corresponding to the shape of the adsorbent in which a plurality of corner portions are formed in the skirt portions and the bond areas are formed at at least two corner portions among the corner portions of the film or films.
With this, the bond areas can be formed at corner portions of a film having, for example, a rectangular shape, and at least two dispersing openings can be formed between each bond areas at the skirt portions of the film or films.
Further, the present invention provides the construction that the film or films have a rectangular shape having left and right sides being parallel to each other and the bond areas are formed at both the left and right sides. With this, the bond areas can be formed continuously at left and right sides of the film or films.
Further, the present invention provides the construction that the film or films are made of an elongated strip-like resinous film and adsorbents are arranged with intervals inside the elongated resinous film or films.
With this, a plurality of film or films can be formed by using an elongated resinous film, and the adsorbent can be received individually in the film or films formed by cutting the resinous film at predetermined intervals.
Further, according to the present invention, a plurality of cut lines are formed in the elongated resinous film at positions between individual adsorbents to define the film or films. With this, a plurality of film or films can be formed by using elongated resinous film or films in which it or they can be cut off at the positions of cutting lines, and the adsorbent can be received individually in the film or films which are defined by the cutting lines in the resinous film.